The first waves of arrests in the deadly siege at the United States Capitol targeted easy targets. Dozens of members of the pro-Trump mob openly boasted about their actions on social media on January 6, and their actions were captured in shocking footage broadcast live by national news outlets.

However, six months after the uprising, the Justice Department is still looking for scores of rioters, despite the fact that the first of more than 500 people arrested has pleaded guilty. The struggle reflects the massive scope of the investigation and the arduous work that authorities still face in the face of an increasing effort by some Republican lawmakers to rewrite what happened that day.

The person who planted two pipe bombs outside the offices of the Republican and Democratic national committees the night before the melee, as well as many people accused of attacks on law enforcement officers or violence and threats against journalists, are among those who have yet to be apprehended. The FBI website, which is looking for information about those involved in the Capitol violence, contains over 900 photos of roughly 300 people labeled “unidentified.”

Part of the problem stems from the fact that authorities made very few arrests on January 6. Instead, they were intent on ridding the building of members of the massive mob that had attacked police, damaged historic property, and combed the halls for lawmakers they threatened to kill. Federal investigators are being forced to go back in time and track down participants.

Since then, the FBI has received numerous tips and pieces of digital media from the general public. However, a tip is only the first step in a lengthy process that includes things like search warrants and interviews to confirm people’s identities and presence at the insurgency in order to file a case in court. And because this was many of the attackers’ first encounter with the law, authorities have no record of them.

The FBI has been assisted by “sedition hunters,” or armchair detectives, who have banded together to identify some of the most elusive suspects, using crowdsourcing to sift through the massive trove of videos and photos from the attack.

A distinctive piece of clothing can sometimes assist the group in making a match. According to Rogers, in one case, a woman carrying a unique iPhone case on Jan. 6 had previously been photographed with the same case at another protest.

John Scott-Railton is a senior researcher at the University of Toronto’s Citizen Lab who has been working with journalists and others to identify suspects using digital clues. While much is known about the “small fish” who committed crimes that day, he believes that a deeper understanding of the actions of organized group leaders is required.

Many of those wanted are accused of violent attacks on police officers. The FBI released a video in which an unidentified man attacks officers with a baton. In another, a man is seen ripping the gas mask off an officer who screamed in pain as the angry mob crushed him into a doorway.

The FBI has offered a reward of up to $100,000 for information leading to the arrest of the person responsible for the pipe bombs that were planted in Washington on January 5.  Footage shows a person in a gray hooded sweatshirt, a mask, and gloves appearing to place one of the explosives under a bench outside the Democratic National Committee, and the person walking in an alley near the Republican National Committee prior to the bomb being placed there. It is unclear whether the bombs were related to the insurgency planning.

According to Justice Department officials, arresting everyone involved in the insurgency remains a top priority. Authorities recently arrested the 100th person accused of assaulting law enforcement, as well as the first person accused of assaulting a member of the press — a man accused of tackling a cameraman, according to prosecutors.

More than a dozen defendants pleaded guilty on January 6, including two members of the Oath Keepers militia group who admitted to conspiring with other extremists to prevent President Joe Biden’s victory from being certified.

The majority of the other plea deals reached so far have been in cases where defendants were only charged with misdemeanors for illegally entering the Capitol. The only defendant who has received a sentence is an Indiana woman who pleaded guilty to a misdemeanor and was not sentenced.